The present invention relates to an automatic sample treatment apparatus which is used in an analyzing apparatus, such as a gas chromatograph, a liquid chromatograph, and a spectrum analyzing apparatus.
In case a sample is analyzed in the analyzing apparatus, such as a gas chromatograph, usually, it is operated such that a syringe, which has the same structure as in an injector or a syringe as a medical instrument, sucks or draws a predetermined amount of a sample from a sample bottle or vial. In order to analyze a plurality of samples continuously, there is used an automatic sample treatment or injection apparatus, wherein a syringe is disposed above a tray holding a plurality of vials, and the predetermined vials are consecutively and automatically transferred to a position in which the syringe can suck a sample.
A structure of a main part of the automatic sample treatment or injection apparatus described above is shown in FIGS. 3(a) and 3(b). FIG. 3(a) is a front view of a conventional automatic sample injection apparatus, and FIG. 3(b) is a side view thereof.
The automatic sample injection apparatus is formed of a syringe 11; a syringe driving section 12 for vertically moving the syringe 11; a tray 24 for holding a plurality of vials 13; and a tray driving section 15 for slidingly transferring the tray 24. The syringe 11 is formed of a barrel 111; a needle 112 attached to a distal end of the barrel 111; and a plunger 113 inserted and fitted in the barrel 111. By a plunger driving section 19, the plunger 113 is pushed into or pulled out of the barrel 111. The tray driving section 15 is formed of a stepping motor 151; a pinion 152 fixed to a rotation axis of the stepping motor 151; and a rack 153 which is provided in the tray 24 and engaged with the pinion 152. Also, a slit 241 is formed at an end portion of the tray 24, and in order to detect the slit 241, a home position sensor 26 including a light emission section and a light receiving section is provided in a predetermined position. Further, a vial detecting sensor 17 is disposed in front of the tray 24 to be vertically aligned with the syringe 11 (FIG. 3(a)).
Operations of the automatic sample injection or treatment apparatus are as follows. Firstly, the tray 24 is moved to a predetermined standard position, i.e. home position, by the tray driving section 15. At this time, light emitted from the light emission section of the home position sensor 26 is reflected at a lower end surface of the tray 24, and the returned light is detected at the light receiving section, so that a position in which the reflected light is not received or obtained due to the slit 241 is recognized as a home position.
Thereafter, a pulse signal with a number corresponding to an amount of transfer from the home position to a desired vial position is applied to the stepping motor 151, so that the tray 24 is transferred. The vial detecting sensor 17 includes a light emission section and a light receiving section as in the home position sensor 26, wherein light emitted from the light emission section hits the vial for reflection, and the reflected light is detected at the light receiving section so as to determine the presence of the vial. After the tray 24 is transferred to locate the desired vial at the sample suction position just under the needle 112, if the vial detecting sensor 17 determines that there is a vial, the syringe driving section 12 lowers the syringe 11, so that the needle 112 is inserted into the vial 13. Then, the plunger 113 is pulled by the plunger driving section 19, and a liquid sample in the vial 13 is sucked into the barrel 111.
However, in the conventional automatic sample injection apparatus, since the transfer of the tray 24 is operated according to a relative position based on the home position, in case the stepping motor 151 becomes out of tune due to factors, such as an external force or load fluctuation of the tray 24, the following problems will occur.
FIGS. 4(a) through 4(d) show a relationship between the vial position and the detected signal of the vial detecting sensor, wherein FIG. 4(a) is a top plan view of the vial; FIG. 4(b) is a side section view of the vial; FIG. 4(c) shows an output at the light receiving section of the vial detecting sensor 17; and FIG. 4(d) shows a vial detecting signal obtained on the basis of the outputs of the light receiving section.
An opening on the upper surface of the vial 13 is smaller than an outer diameter of a lower part thereof, and at the opening on the upper surface, a septum 131 is tightened or attached by a resinous cap 132. An outer shape of the vial 13 is a column-like shape, and since the reflected light becomes weak as the position of the vial with respect to the vial detecting sensor 17 is deviated from a center of the vial, the output signal of the light receiving section of the vial detection sensor 17 provides a curve as shown in FIG. 4(c). By comparing the light receiving signal with a decision threshold which is set preliminarily, the detected signal showing a presence of a vial is formed as shown in FIG. 4(d).
In order to absorb a dispersion or deviation of the positions at the time of moving the tray 24 due to the individual difference of the apparatus or the like, it is required that the decision threshold is set at a comparatively low level so as to decide that there is a vial even if the position of the vial 13 is slightly deviated. Therefore, a range B for detecting a vial is wider than a sample absorbable range A, i.e. range in which the sample can be sucked, which substantially corresponds to the diameter of the opening of the upper surface of the vial 13.
As a result, in case the stepping motor 151 becomes out of tune and a deviation of X in the amount of transferring the tray 24 occurs, suction of a sample might be impeded. Namely, in case of X&lt;A/2, suction is possible; but in case of A/2.ltoreq.X.ltoreq.B/2, it becomes highly possible that the needle 112 strikes the cap 132 of the vial 13 to cause bending of the needle. In case of B/2&lt;X, the existence of the vial 13 itself can not be detected. When the needle 112 is broken, analysis thereafter can not be operated to cause extreme hinderance. Needless to say, there is also a problem such that it takes time to change the syringe 11 and it requires an additional cost.
Accordingly, the present invention is directed to solve the aforementioned problems, and an object of the present invention is to provide an automatic sample treatment or injection apparatus in which at the time of sucking the sample, a needle of a syringe can surely pierce a center of a septum of a vial, and especially, even if the stepping motor for driving the tray becomes out of tune, it can be prevented that the needle hits or strikes the vial itself.
Further objects and advantages of the invention will be apparent from the following description of the invention.